The all-encompassing Mr Webster does include the following without italics, although it is certainly getting into the technical vocabulary of philosophy in a big way (but hey, doesn't that make a nice change from chemistry
?).
Main Entry: ar·che
Function: noun
Inflected Form(s): plural ar·chai \-kimacr\
: something that was in the beginning : a first principle: a in early Greek philosophy : a substance or primal element b in Aristotle : an actuating principle (as a cause)
"arche." Webster's Third New International Dictionary, Unabridged. Merriam-Webster, 2002.
http://unabridged.merriam-webster.com (23 Sep. 2007).
